Methyl (2R,4S)-4-aminopyrrolidine-2-carboxylate, N1-BOC protected, N-a-butoxycarbonyl-trans-4-amino-L-prolinemethyl ester, trans-4-amino-N-tert-butoxycarbonyl-D-proline methyl ester; (2R,4S)-1-tert-Butyl 2-methyl 4-aminopyrrolidine-1,2-dicarboxylate;